The purpose of the research is to investigate longitudinally the relationship between physical maturation and adjustment during early adolescence. The biological and role changes, in general, and the timing of these changes, in particular, may exacerbate existing emotional difficulties, create new problems that result in acting out and delinquent behavior, or even lead to psychopahtology. The research focuses on two interrelated objectives: (a) the examiniation of the relationships between the timing of maturation, using more precise measures of pubertal status than have been used in previous research, and adjustment; and (b) the examination of the sequence of reciprocal relationships among hormonal and physical changes and psychological development. Participants will include male and female 9- to 17-year-old adolescents, their parents, and peers. Each participant will be evaluated for stage of pubertal development. Psychological assessments will include standardized psychological tests and systematic observation.